A conveyor is often installed in a delivery center, a pickup point, or a warehouse. For example, in the delivery center, it is necessary to assort objects according to delivery destinations. Thus, in the conveyor installed in the delivery center, a conveying passage is divided into many branch conveying passages. That is, the conveyor installed in the delivery center often includes a plurality of delivery target places.
In the conveyor installed in the delivery center, a plurality of primary branch conveying passages branch of from a main conveying passage. Further, secondary branch conveying passages and tertiary branch conveying passages further branch off from the primary branch conveying passages.
The conveyor installed in the delivery center includes a plurality of straight conveying passages which constitute the main conveying passage, the primary branch conveying passage and the secondary branch conveying passage, and a conveying direction changing device which changes a conveying direction. The conveying direction changing device is disposed in a branching point.
When objects are conveyed using a conventional conveyor, a storage medium such as a bar code or an IC tag in which information of a conveyance destination (target place) is written is attached to each of the objects. Further, an information read-out device is disposed on each branching point to read the conveyance destination of an object, and the conveying direction changing device is operated to send out the object to a predetermined conveying passage.
There is known a continuous conveyor that includes many zones (Patent Document 2).
In the conveyor disclosed in Patent Document 2, a zone controller is provided in each zone, and a motor of each zone is controlled by the zone controller.
Further, there is also known a conveyor that includes a zone having a branching function (Patent Document 3).
In the conventional technique, in the zone having a branching function, a branching operation is performed upon receiving a signal from the outside.
That is, the zone having a branching function has the function of moving an object straight forward and discharging an object in the lateral direction.
These operations are executed by operating a plurality of motors in a predetermined order. In the conventional technique, the motors are sequentially operated in response to signals from the outside.
Specifically, the zone having a branching function is controlled by a programmable logic computer (PLC).